Terminal resistor for waveguides and coaxial high frequency cables

ABSTRACT

A terminal resistor or load for waveguides and coaxial high frequency cables; the resistor being formed from selected electrically conductive synthetic resin materials. Such resistors or loads being distinguished by being frequency independent; meeting exacting absorption properties; and retaining its effectiveness under extreme conditions of mechanical wear and tear.

United States'Patent [191 Prinzhorn [451 July 17,1973

[ TERMINAL RESISTOR FOR WAVEGUIDES I AND COAXIAL HIGH FREQUENCY CABLES[75] Inventor: Klaus Prinzhorn, Burgdorf, Germany [73] Assignee:Knbelund Metallwerke Gutenholfnungshutte Aktiengesellschaft, Hanover,Germany [22] Filed: May 10, 1972 [21] Appl. No.: 251,870

[52] U.S. Cl 333/22 R, 252/502, 252/511 [51] Int. Cl. H01]: 1/26 [58]Field 01 Search 252/502, 503, 511,

[56.] References Cited 7 9 UNITED STATES'PATENTS 2,968,775 l/196l Rose333/22 R X 3,104,985 9/1963 Williams et a1. 252/511 X 3,155,631 11/1964Z PP Jr 252/511 X 2,765,354 10/1956 Carpenter et 81.. 252/502 X3,208,013 9/1965 Walker et al. 252/502 X 2,977,591 3/1961 Tanner 333/22R X 3,036,280 5/1962 Woodcock 333/22 R 2,730,597 1/1956 Podolsky et al333/22 R Primary Examiner-Rudolph V. Rolinec Assistant Examiner-SaxfieldChatmon, .lr. Atlorney-Philip G. Hilbert [5 7] ABSTRACT A terminalresistor or load for waveguides and coaxial high frequency cables; theresistor being formed from selected electrically conductive syntheticresin materials. Such resistors or loads being distinguished by being.

frequency'independent; meeting exacting absorption properties; andretaining its effectiveness under extreme conditions of mechanical wearand tear.

6 Claims, 4 Drawing Figures Ill/l/l/ll/l/l/ll/l/l/l/l/l/ PAIENIEB JUL x1 ma /1O LII/ll- TERMINAL RESISTOR FOR WAVEGUIDES AND COAXIAL HIGHFREQUENCY CABLES This invention relates to a terminal resistor which isto be used in conjunction with waveguides and coaxial high frequencycables. Such devices are particularly useful in the transmission ofelectromagnetic waves of very high frequency.

.Such terminal resistors or loads serve for reflectionless terminationof waveguides or high frequency cables and therefore they must showminimal reflection factors, while at the same time being operable withinthe largest possible range of frequencies. A further requirement of suchloads is that they should be largely independent of the direction ofpolarization and of the incidence of the impinging wave.

There are known loads which are formed of wood with rotationallysymmetrical configurations such as conesor cylinders with a conicalbore. These loads have a length of about ten conductor diameters, whichmakes them unsuitable for field use as at proving grounds, inasmuch asthey are unwieldy.

Another know load device is formed of carburized paper (Bakelized paper)in strip form which cut V shaped and two of which are arranged at rightangles to each other with their apex lying at the conductor wall. Suchloads can not satisfy exacting requirements.

,Yet another load device known in the art is formed from a mixture ofsynthetic resin and carbonyl iron dust. This type of load is best suitedfor low reflection factors. However such load is expensive to fabricateand is quite brittle making it unsuitable for field testing,

since under adverse conditions, it fails with even small appliedstresses.

Accordingly, an object of this invention is to provide an improvedterminal resistor or load which is frequency independent; which showsoptimum absorption characteristics; which is simple to fabricate; andwhich retains its effectiveness under adverse operating conditions.

A further object of this invention is to provide a terminal resistor orload of the character described, which is fabricated from anelectroconductive polyethylene plastic which is of an eleasticcharacter; the device being unaffected in its operationalcharacteristicsunder extreme conditions of mechanical wear and tear.Other objects of this invention will in part be obvious and in parthereinafter pointed out.

DESCRIPTION OF THE DRAWING DESCRIPTION OF THE PREFERRED EMBODIMENTS Ithas been found that resistors or loads for wave guides or coaxialcables, formed from selected thermoplastic materials which are renderedelectroconductive, show improved results in the microwave region and ishighly resistant to adverse conditions of use, particularly in fieldtesting.

Thus, the loads of the instant'invention are formed from a compositionconstituted of polyethylene, a polyethylene copolymer and a conductivematerial such as carbon black or the like.

The composition is made up of 100 parts of polyethylene, from 20 to 40parts of a polyethylene copolymer, and from 50 to 100 parts ofconductive carbon black, all by weight. Preferably 30 parts of thecopolymer and parts of carbon black are mixed with the parts ofpolyethylene.

The copolymer may be made up of either ethyle vinyl acetate or anacrylate such as ethylene acrylate copolymerized with the polyethylene.

The resultant composition is suitably molded in the desiredconfiguration, forming the resistor or load to be used with a wave guideor a coaxial cable.

Thus, as shown in FIGS. 1, 2, a wave guide generally indicated at 10,having a wall 11 and terminal end 12, is adapted to have associatedtherewith a load embodying the invention and generally indicated at 13.The load 13 may take the form of a hollow conical member 14 formed ofthe above described composition. A support member 15 is fixed to thebase of load member 14 and removably mounted in the open end 12 of waveguide 10 for testing purposes.

Alternatively, the load of the instant invention may be applied tocoaxial cables 10A, as shown in FIGS. 3, 4. Here the inner conductor isindicated at 16 and the outer conductor at 15A. The load 13A is similarto load 13, being in hollow conical form with member 14A with an apexopening 17 to pass the terminal end portion of inner conductor 16therethrough. The member 14A is fixed to support member 15 and ismounted in the open end 12A of outer conductor 15A.

It is understood that the loads 13, 13A may take other geometricalconfigurations and may be solid as wellas hollow. Such loads have beenfound to be frequency independent, particularly in the microwave regionand almost completely free of reflection so that it can be regarded as amatching load. The particular configuration of the load is related tothe waves to be transmitted, that is, which and how many planes ofpolarization are present in the wave guide.

I claim:

1. A terminal load for means for transmitting high frequencyelectromagnetic waves, said load comprising a resilient member formedofa composition consisting of 100 parts of polyethylene, 30 parts ofpolyethylene copolymer, and 70 parts of carbon black, all by weight.

2. A load as in claim 1 wherein said copolymer is ethylene vinylacetate.

3. A load as in claim 1, wherein said copolymer is ethylene acrylate.

4. Aload as in claim 1, wherein said member is of hollow conical shape,and further including a support member fixed to the base of said member.

5. A load as in claim I, wherein said transmitting means comprises awave guide.

6. A load as in claim 1, wherein said transmitting means comprises acoaxial cable.

2. A load as in claim 1 wherein said copolymer is ethylene vinylacetate.
 3. A load as in claim 1, wherein said copolymer is ethyleneacrylate.
 4. A load as in claim 1, wherein said member is of hollowconical shape, and further including a support member fixed to the baseof said member.
 5. A load as in claim 1, wherein said transmitting meanscomprises a wave guide.
 6. A load as in claim 1, wherein saidtransmitting means comprises a coaxial cable.